To the disappointment of salivating headline writers everywhere, Paul Clarke and Helen Adams will not have sex on national television this week - and it's probably just as well.

The last thing British viewers want is sex rammed down their throats. The moment that furtive fumbling in the Big Brother love nest turns into a full-on squelch fest, the nation will turn off.

Helen will be branded a slag and Paul attacked as a Lothario. We want a love story, not a porn film.

Anyway, sex between Paul and Helen would simply be wrong: for weeks we have watched them chase each other like a pair of fifteen-year-olds. They are just not big enough for blow jobs.

Mark Frith, editor of the entertainment bible Heat magazine, says viewers would be turned off if they did anything as grown-up as sex: "Theirs has been a sweet innocent courtship - they remind me nothing more of two kids in the playground.

"Today I was watching them playing on the sofa, lying upside down. They were doing what you do when you're kids, looking at your house upside down and going 'wow'. It's so sweet.

"For every reference to sex they make there are ten times when they are being young and kidlike. I think that there is something about Paul and Helen rather than about us being British that makes us not want to see them having sex."

Peter Bazalgette, creative director of Endemol Entertainment, the production company behind the show, agrees. "I am enjoying the 'will they, won't they' game so much that I would personally be rather disappointed if it was resolved."

While some Channel 4 sources indicate the broadcaster is worried that sex in Big Brother could turn off the audience, Bazalgette says that he was far more concerned that this year's show would not produce a Big Event.

Viewing figures would bounce along around the bottom of expectations, and the show would end up a damp squib. "It's not as good as last year," people would complain.

The Paul and Helen saga has changed that: and now their joint nomination has forced it to a dramatic conclusion. It is this year's equivalent of Nasty Nick: a story the viewers - and the newspapers - can get their teeth into.

Once the relationship is consummated, it would be a disaster. Not that the producers of Big Brother are worried about what the Daily Mail might say the next day: they know that most of the programme's viewers have a relaxed attitude towards sex.

Rather, their best story would be spoiled, the drama killed. We have been here before. In an earlier version of the show in Holland, eventual winner Bart was filmed having sex with fellow housemate Sabine.

It happened after a similar courtship, and in the week that they were both nominated for eviction. Bazalgette doubts, however, that the Paul and Helen situation will go in the same direction.

"I think the romance is fantastic, charming, I rather like them both. And what will be will be, but I would be very surprised if there was a sexual act in the house."

It has almost happened several times - particularly in the past week. But on every occasion, either Paul or Helen has pulled back from the brink. Paul is concerned about interfering in what he perceives as Helen's existing relationship, while Helen is worried about how she will be perceived.

Bazalgette believes, however, that it would not be bad for the show if the couple do get it together.

"The point is, people imagine that the sex would be glossy, like in a film or in a TV drama. But we are not into making movies. If there is ever sex in the Big Brother house all you will see is a static duvet in the distance."

And while there may be an outburst of what Bazalgette terms "suburban hypocrisy", he does not believe that most of the viewers would care.

"They are mostly under 30, for whom nudity, sexual proclivity, colour are not a problem. None of these are issues for them. Some people may not like it, but if there ever was sex, it would be part of a pattern. People are much less afraid of it now."

Frith agrees: "I don't think it would be a problem. It's going to take more than that. It would be done discreetly anyway I'm sure. I don't think it would be graphic. There is maybe something bout being British but it's more an awareness that they're being watched."

Broadcasters know this very well - and they've developed a new style of programmes to cope with the demand. It's called porn with a purpose - and it's pretty simple.

All you have to do is dress up a load of titillating footage, splice in a psychologist and call it a documentary. Big Brother is probably the simplest example of the genre.

Yet Bazalgette points out that sex is not the sole point of Big Brother. If it was, why fill the house with three or four people in stable relationships and include only one gay man (Josh entry later was not guaranteed - he was voted in from a choice of three)?

Instead, he says, Channel 4 is more concerned with tapping into a zeitgeist: "They want the most interesting, iconic people of their generation. If we wanted lots of sex we would have got a load of ex porn-stars and page three models."